1. Field of the Invention
The present invention generally relates to additives for stabilizing organic products that are subjected to oxidative, thermal, and/or light-induced degradation. More particularly, the present invention relates to a class of acridan derivatives useful as antioxidants.
2. Description of Related Art
The stabilization of organic materials with antioxidants or other stabilizers is well known to those skilled in the art. For example, in developing lubricating oils, there have been many attempts to provide additives that impart, for example, antioxidant, antiwear, and deposit control properties thereto. Zinc dialkyldithiophosphates (ZDDPs) have been used as antifatigue, antiwear, antioxidant, extreme pressure and friction modifying additives for lubricating oils for many years. However, ZDDPs are subject to several drawbacks due to their zinc and phosphorus content. The presence of zinc, for example, contributes to the emission of zinc-containing particulates in the exhaust, which potentially presents toxicological and environmental issues. Also, when phosphorus-containing lubricating oil compositions are introduced into the combustion reaction of an engine, phosphorous enters the exhaust stream where it acts as a catalyst poison for catalytic converters. In this manner, phosphorous is suspected of limiting the service life of the catalytic converters that are used on cars to reduce pollution.
Thus, it is important to limit the formation of particulate matter and pollution during engine use for toxicological and environmental reasons, while maintaining the antioxidant properties of the lubricating oil.
It would therefore be desirable to provide improved additives for stabilizing organic products that are subject to oxidative, thermal, and/or light-induced degradation and in need of stabilization to prevent or inhibit such degradation, e.g., additives for lubricating oils that can improve the antioxidant properties of the oil.